Which sentence is correctly punctuated.

Question

1. The cost, and size of computers are decreasing, almost as rapidly as processing power is increasing.
2. Database management systems were originally large, unwieldly, and ready to use.
3. A factory closing means the community loses jobs tax revenues and retail sales.
4. An operating system is the set of instructions, that directs the overall operations of the computer.

1. comma after "cost" isn't needed
2. series -- http://grammar.ccc.commnet.edu/grammar/commas.htm
3. series -- http://grammar.ccc.commnet.edu/grammar/commas.htm
4. comma after "instructions" isn't needed

So you decide between 2 and 3.

=)